Light record applying near field light has recently attracted attention as a method for achieving an increase in density of an optical recording apparatus. In accordance with the above, studied has been mounting of a near field light generation element to an optical head in an optical recording apparatus.
Development of optical recording apparatuses with high density has aggressively progressed in accordance with a recent explosive increase in quantity of information such as an image and a moving picture. It has been known that an optical disc represented by a CD (a compact disc) and a DVD (a digital versatile disc) has a limited recording density due to a limit of diffraction of light. In order to exceed the limit, proposed have been a method of using light with shorter wavelength and a method of using near field light. The optical recording apparatus using near field light uses a method of making light incident on an optical minute aperture whose size is less than the wavelength, letting near field light, which is slightly spread from the aperture, and a surface of a recording medium operate mutually and detecting permeated or reflected scattering light to read out a minute data mark. A smallest mark size capable of record and reproduction is not defined by a wavelength of the incident light but by a size of the opening. Accordingly, making a minuter aperture allows the density of record to be improved. The aperture is necessary to be close to the surface of a recording medium in an optical recording apparatus using the near field light. Further, the aperture is required to scan the surface of the recording medium at high speed for the purpose of achieving high data transmission speed.
A flying head method, which is used for conventional magnetic record, has been typically proposed in order to meet the above requirements. As described in Patent Reference 1, for example, studied has been a near field light generation element having an optical minute aperture whose size is less than the wavelength of the incident light, the near field light generation element for generating near field light by radiating the incident light on the minute aperture. The minute aperture is formed so that a part of an outline of the aperture would be crossing at substantially right angles with a polarization direction of the incident light. This causes only a part of the outline of the minute aperture, the part crossing at substantially right angles with the polarization direction of the incident light to generate near field light having high intensity, so that high resolution and high optical efficiency can be achieved.
Moreover, as described in Patent Reference 2, on a surface, which is faced to the recording medium, of an optically transparent floating slider, provided closely to each other are a columnar or square pillar-shaped pad provided for controlling a condition of contact or floating between the slider and the recording medium and a probe for generating near field light having a minute spot size. Further, the pad and the probe are made substantially equal in height from a surface facing the information recording medium of the slider while the height from the surface of the probe, the surface facing the information recording medium, is made lower than the height from the surface of the pad, the surface facing the information recording medium. This causes a near field optical head and the slider to be formed into one body, and thereby, allows a near field optical head having a small-sized, lightweight and simple structure, the near field optical head having similar performance to that of the head used in a conventional magnetic disc apparatus, to be obtained. Furthermore, relative speed between a recording medium and an optical head for recording and reproducing information can be increased since the slider is small in size and light in weight. In addition, it is possible to generate the near field light having a minute size by forming an optically opaque thin film, a metal thin film, for example, on the pad and the probe in the near field optical head or by forming a minute aperture, which has a structure that a material forming the probe is exposed at a top end part of the probe and in which a surface of a part where the probe is exposed is in a plane substantially same as a surface of the metal thin film.
Further, in a magnetic recording apparatus, density in recording information in a single recording surface has increased recently in accordance with an increase in capacity of a hard disc and such in a computer apparatus. Surface record density should be increased in order to increase recording capacity per a magnetic disc, for example. A recording area per a bit in a recording medium, however, decreases according to an increase in record density. A decrease in size of a bit causes potential energy of a record of information of a bit to get closer to heat energy in a room temperature. Accordingly, occurs a problem of heat demagnetization such as reversal and disappearance of recorded information due to thermal fluctuation and the like.
An in-plane recording system, which has been generally used, is a system of recording magnetism so that a direction of magnetization would be faced to an in-plane direction of a recording medium. In this system, however, easily occurs the above-mentioned disappearance of recorded information and such due to heat demagnetization. Accordingly, the system is changing to a perpendicular recording system in which a signal of magnetization is recorded in a direction vertical to a recording medium for the purpose of solving such a disadvantage. The perpendicular recording system is a system in which magnetic information is recorded in a recording medium according to the principle that a single magnetic pole is brought close. The recording magnetic field is faced to a direction substantially vertical to a recording film in accordance with the perpendicular recording system. Information recorded in a vertical magnetic field is easy to keep stability in energy since it is difficult for the pole N and the pole S to form a loop in a surface of the recording film. Accordingly, the perpendicular recording system has a more tolerance to heat demagnetization than the in-plane recording system.
Recent recording media, however, are required to have further higher density according to the need for recording and reproducing a greater quantity of information having higher density. In order to meet the requirement, introducing has been a recording medium having a great coercivity for the purpose of keeping influence of adjacent magnetic sections and thermal fluctuation to a minimum. This makes record of information in a recording medium difficult even in the case of the above-mentioned perpendicular recording system.
In order to solve such a disadvantage, proposed has been a hybrid magnetic recording system (a near field light assisted magnetic recording system) in which near field light is used to locally heat a magnetic section and temporarily reduce the coercivity while writing is carried out. The hybrid magnetic recording system is a system of using the near field light generated by an interaction between a minute area and an optical aperture (Patent Reference 3, for example) formed in the near field optical head into a size smaller than the wavelength. Using the minute optical aperture overstepping a limit of diffraction of light, namely, the near field optical head including the near field light generation element, as described above, allows an area in an area lower than a wavelength of light, the wavelength being a limit in a conventional optical system, to be heated. Accordingly, the density of a recording bit can be made higher than that of a conventional optical information recording and reproducing device.
In the case of using a magnetic recording head having such a structure, the near field light is generated while the recording magnetic field is simultaneously applied so that various kinds of information would be recorded in the recording medium. That is to say, cooperation between the near field light and the magnetic field enables record in a recording medium to be achieved.    Patent Reference 1: JP-A-2002-092276    Patent Reference 2: JP-A-11-265520    Patent Reference 3: WO-2007/074650